ES3036062T3 - Led filament - Google Patents

Abstract

The present invention relates to an LED filament (10), comprising: a carrier (12) comprising a first elongated carrier portion (14a) with first LEDs (16a), a second elongated carrier portion (14b) with second LEDs (16b), and a third elongated carrier portion (14c) with third LEDs (16c), the third elongated carrier portion being arranged between the first elongated carrier portion and the second elongated carrier portion, wherein the carrier is folded along a first longitudinal folding line (15a) separating the first and third elongated carrier portions and along a second longitudinal folding line (15b) separating the second and third elongated carrier portions into a three-sided structure, for example in the shape of a triangle. (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

LED filament

Field of the invention

The present invention relates to an LED (light emitting diode) filament, a lamp comprising at least one such LED filament, and a method of manufacturing an LED filament.

Background of the invention

Incandescent light bulbs are rapidly being replaced by LED-based lighting solutions. However, users appreciate and desire replacement lamps that resemble incandescent bulbs. To achieve this, one can simply utilize the infrastructure for producing glass-based incandescent lamps and replace the filament with LEDs that emit white light. One concept is based on LED filaments placed in such a bulb. The appearance of these lamps is highly appreciated, as they are very decorative.

US2019017657 describes a filament-type light-emitting diode (LED) light source that includes a plurality of LED modules, a coupler, and a common connecting portion. The LED modules are in a polygonal prism structure and emit white light having different color temperatures or light of different wavelengths. The polygonal prism structure may be a triangular prism. Each LED module has a bar shape on a respective side surface of the polygonal prism structure and includes a first connecting electrode and a second connecting electrode. The coupler couples the LED modules to maintain the polygonal prism structure. The coupler may be on an edge of the polygonal prism structure to couple adjacent ones of the plurality of LED modules. The coupler/coupling member may be made of a material having bonding properties. For example, the coupling member may be an adhesive polymer.

However, one problem with the filament-type LED light source is that it can be difficult/cumbersome/time-consuming to manufacture/assemble.

Document US2018106434 describes a light-emitting diode lighting device comprising a light-transmitting encapsulant, a transparent core, a stereoscopic light source board structure, and a power supply device. The stereoscopic light source board structure is constituted by a plurality of connecting secondary light source boards. The stereoscopic light source board structure installed in the light-transmitting encapsulant is connected to the transparent core and supported by the transparent core. The secondary light source board comprises a circuit board body and a light-emitting diode mold installed on a surface of the circuit board body by surface-mount technology.

Summary of the invention

It is an objective of the present invention to overcome this problem and provide an improved LED filament.

According to a first aspect of the invention, this and other objects are achieved by an LED filament, comprising: a carrier comprising a first elongated carrier portion, a second elongated carrier portion, and a third elongated carrier portion arranged side by side, the third elongated carrier portion being provided between the first elongated carrier portion and the second elongated carrier portion; first LEDs mounted on a first surface of the first elongated carrier portion to provide light for the first LED filament; second LEDs mounted on a corresponding second surface of the second elongated carrier portion to provide light for the second LED filament; and third LEDs mounted on a corresponding third surface of the third elongated carrier portion to provide light from the third LED filament, wherein the carrier is folded along a first longitudinal fold line separating the first elongated carrier portion and the third elongated carrier portion and along a second longitudinal fold line separating the second elongated carrier portion and the third elongated carrier portion into a three-sided structure.

The third LED filament light may have a different spectrum than the first LED filament light and/or the second LED filament light, e.g., a different color and/or color temperature than the first LED filament light and/or the second LED filament light. Alternatively or complementarily, the third LED filament light may have a different CRI than the first LED filament light and/or the second LED filament light.

The present invention is based on the understanding that by folding the carrier into a three-sided structure, e.g., a triangular shape, instead of applying an adhesive between separate LED modules as in US2019017657, the manufacturing of the LED filament can be simplified and/or made more efficient. Furthermore, by folding the carrier into a triangular shape, the appearance of the LED filament becomes small (i.e., the LED filament looks thin/narrow/narrow) and the optical interference between the first/second/third LEDs can be low.

As indicated above, the carrier is preferably folded into a triangular shape. In other words, the carrier can be folded approximately 120 degrees along the first and second longitudinal fold lines such that the carrier has (obtains) a triangular cross-section. The folded carrier could also be described here as a triangular prism structure with a hollow center. The three outer sides of the triangular shape/triangular cross-section/triangular prism structure can be formed by the first to third surfaces on which the different LEDs are provided. Alternatively, the carrier could be folded approximately 90 degrees into a U-shape.

The carrier can be perforated with holes along the first and second longitudinal fold lines. This can relieve tension on the fold lines. The holes can be achieved using laser cutting.

Each of the first elongated carrier portion and the second elongated carrier portion comprises notches configured to allow the LED filament to be arranged in a non-straight configuration. The non-straight configuration can be a curved configuration, such as a ring, a 2D spiral, a 3D spiral, or a helix. By means of the notches, the folded LED filament carrier can be folded into the non-straight configuration without deformation. Specifically, with the carrier folded in the shape of a triangle, the radius of curvature for the second central portion is still over the thickness of the carrier, but for the first and second outer portions, the radius of curvature passes through the axial width. Without the notches, tensile stress and compressive forces in the material would deform the bent carrier into an irregular shape, leading, for example, to an irregular spiral shape of the LED filament when mounted in a lamp's pump stem. However, with these notches, space is provided for the material of the first and second carrier portions to bend over the width of the LED filament. The pulling and pushing forces can be eliminated or minimized to a level where deformation of the LED filament is acceptable when assembled. Alternatively, not in accordance with the invention, the LED filament could be arranged in a straight configuration, such that the notches can be omitted.

The notches can be placed at regular intervals along the length of the carrier. This can allow the LED filament carrier to be curved appropriately with a constant radius of curvature. Alternatively, the notches could be placed at irregular intervals along the length of the carrier. For example, there could be a higher density of notches at the beginning of the LED filament than at the end (e.g., when the radius of curvature of the LED filament varies along the length of the LED filament).

Each notch of the first elongated carrier portion may extend from a first longitudinal edge of the first elongated carrier portion toward the first longitudinal fold line, wherein each notch of the second elongated carrier portion extends from a second longitudinal edge of the second elongated carrier portion toward the second longitudinal fold line.

Each notch of the first elongated carrier portion may be V-shaped and point to the first longitudinal fold line, wherein each notch of the second elongated carrier portion is V-shaped and points to the second longitudinal fold line.

The legs of each V-shaped notch can meet when the LED filament is arranged in a non-straight configuration. The result is a gentle bending curve of the LED filament, and the notch gap closes.

A first encapsulant segment for at least one of the first LEDs may be provided between every two subsequent notches of the first elongated carrier portion, wherein a second encapsulant segment for at least one of the second LEDs is provided between every two subsequent notches of the second elongated carrier portion. The first and second encapsulant segments may comprise, for example, a luminescent material configured to at least partially convert light from the LEDs into converted light. The luminescent material may be a phosphor, such as an inorganic phosphor and/or quantum dots or rods. The first and second encapsulant segments may specifically be segments of phosphorus-doped silicone layer.

The first encapsulating segments may form a substantially continuous first encapsulant covering the first LEDs, and the second encapsulating segments may form a substantially continuous second encapsulant covering the second LEDs when the LED filament is arranged in the non-straight configuration. That is, the spaces between the silicone layer segments may also be closed. This results in two continuous phosphor layers when the LED filament is viewed.

The first LED filament light may be a first white LED filament light, wherein the second LED filament light is a second white LED filament light of a different color temperature than the first white LED filament light, and wherein the third LEDs are RGB (red green blue) LEDs for emitting the third colored LED filament light. The first LEDs may be, for example, blue and/or UV LEDs on which the first encapsulant segments are provided, while the second LEDs may be blue and/or UV LEDs on which the second encapsulant segments are provided. To this end, by folding the carrier into the three-sided shape, crosstalk that otherwise occurs when the blue light from the RGB LEDs also strikes the phosphors of the first and second encapsulant segments is significantly reduced. In other words, the blue LEDs in the RGB portion of the filament cannot excite the phosphors in the other portions of the filament. The white LED filament light could be a warmer white LED filament light. The second white LED filament light could be a cooler second white LED filament light. The color temperature of the light from the first white LED filament could be, for example, 2,700 K. The color temperature of the light from the second white LED filament could be, for example, 4,000 K. Alternatively, the first, second, and third LED filament lights could all be white LED filament lights (multi-CCT white filaments), where the blue of one CCT (e.g., a cool white channel) cannot activate the phosphor in a neighboring (warmer) white channel, so it does not change the CCT of the neighboring channel. In another alternative, the RGB LEDs could be mounted on one of the outer elongated carrier portions (i.e., on the first elongated carrier portion or the second elongated carrier portion), while the LEDs for the first and second white LED filament lights are mounted on the middle/third carrier portion and the other outer elongated carrier portion, respectively. The encapsulants/encapsulant segments can be arranged accordingly.

The width w of each of the first, second and third elongated carrier portions may be in the range of 1 - 3 mm, preferably 1.2 - 1.5 mm. The length L of the carrier may be at least 5 times this width (L>5 w).

The carrier can be made of a film. The film can be flexible. The film can be transparent. The film can have a thickness of approximately 0.01 mm. The carrier can be, for example, a film of transparent polyimide carrier (flex).

According to a second aspect of the present invention, there is provided a lamp comprising at least one LED filament according to the first aspect. The lamp may (thus) be an LED filament lamp. The lamp may further comprise a light-transmitting envelope at least partially surrounding said at least one LED filament, and a connector for electrically and mechanically connecting the lamp to a socket. The lamp may be, for example, a replacement bulb.

According to a third aspect of the present invention, there is provided a method for manufacturing an LED filament according to the first aspect, the method comprising: providing the carrier; and folding the carrier along the first and second longitudinal fold lines into a three-sided structure, for example, a triangular shape. This aspect may have the same technical features and effects as the first aspect, and vice versa. It is noted that the invention relates to all possible combinations of features recited in the claims.

Brief description of the Figures

These and other aspects of the present invention will now be described in more detail, with reference to the accompanying Figures showing the embodiment(s) of the invention.

Figure 1 is a cross-sectional view of an LED filament according to one or more embodiments of the present invention.

Figure 2 is a partial perspective view of the LED filament in Figure 1.

Figures 3-4 show notches in the LED filament before and after bending.

Figure 5 is a side view of the LED filament arranged in a helical configuration.

Figure 6 is a side view of a lamp comprising the LED filament.

Figure 7 is a flow diagram of a LED filament manufacturing process.

Figures 8-9 illustrate the manufacturing of the LED filament.

As illustrated in the figures, similar reference numbers refer to similar elements throughout.

Detailed description

The present invention will now be described more fully hereinafter with reference to the accompanying figures, which show the presently preferred embodiments of the invention. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for completeness and completeness, and fully convey the scope of the invention to the skilled person.

Figures 1-2 show a multi-channel LED (light emitting diode) filament 10 according to one or more embodiments of the present invention.

The LED filament 10 comprises a carrier 12. The carrier 12 may have a width W in the range of 3.5-4.5 mm (see Figure 3). The carrier 12 may have a length L. The carrier 12 may have a thickness of approximately 0.01 mm. The carrier 12 may be, for example, a flexible sheet of transparent polyimide carrier.

The carrier 12 comprises a first elongated carrier portion 14a, a second elongated carrier portion 14b, and a third elongated carrier portion 14c. The portions 14a-c are arranged side by side. The third elongated carrier portion 14c is provided between the first elongated carrier portion 14a and the second elongated carrier portion 14b. The first elongated carrier portion 14a and the third elongated carrier portion 14c are defined by a first (longitudinal) fold line 15a. Likewise, the second elongated carrier portion 14b and the third elongated carrier portion 14c are defined by a second (longitudinal) fold line 15b. The width w of each of the first, second and third elongated carrier portions 14a-c may be in the range of 1 - 3 mm, preferably 1.2 -1.5 mm. The length L of each carrier portion 14a-c may be at least 5 times its width w, L>5 w.

The LED filament 10 further comprises LEDs 16a for providing light for the first LED filament 18a. The first LEDs 16a are mounted on a (first) surface 20a of the first elongated carrier portion 14a. The first LEDs 16a may be arranged in a linear array in a longitudinal direction of the first elongated carrier portion 14a. A first electrical circuit 22a may connect the first LEDs 16a. The first electrical circuit 22a may be or form part of a flexible printed circuit (FPC).

The LED filament 10 further comprises secondary LEDs 16b for providing secondary LED filament light 18b. The second LEDs 16b are mounted on a (second) surface 20b of the second elongated carrier portion 14b. The second LEDs 16b may be arranged in a linear array in a longitudinal direction of the second elongated carrier portion 14b. A second electrical circuit 22b may connect the second LEDs 16b. The second electrical circuit 22b may be or form part of a flexible printed circuit (FPC).

The LED filament 10 further comprises third LEDs 16c for providing third LED filament light 18c. The third LEDs 16c are mounted on a (third) surface 20c of the third elongated carrier portion 14c. The third LEDs 16c may be arranged in at least a linear array in a longitudinal direction of the third elongated carrier portion 14c. A third electrical circuit 22c may connect the third LEDs 16c. The third electrical circuit 22c may be or form part of a flexible printed circuit (FPC).

The first, second and third surfaces 18a-c could be considered corresponding surfaces since they are part of, or originate from, the same main surface of the carrier 12, as can be seen in particular in the Figures.

8-9.

In the illustrated embodiment, the first LED filament light 18a is a white LED filament light 18a, preferably warm white WW (e.g., 2700 K), the second LED filament light 18a is a white LED filament light 18b, preferably cool white CW (e.g., 4000 K), while the third LEDs 16c are RGB LEDs for emitting the third colored LED filament light 18c. The first LEDs 16a may be, for example, blue LEDs covered by a first encapsulant 24a comprising phosphors. Likewise, the second LEDs 16b may be blue LEDs covered by a second encapsulant 24b comprising phosphors. The red, green, and blue LEDs of the third LEDs 16c may be arranged in triplets, as shown in Figure 3. The third LEDs 16c may be covered by a third encapsulant 24c. The third encapsulant 24c may be continuous. The third encapsulant 24c may be transparent or dispersed (and free of phosphorus or the like for wavelength conversion). The third encapsulant 24c may be a silicone layer. Each of the first, second, and third encapsulants 24a-c may be domed.

The electrical circuits 22a-c may be configured such that the first LEDs 16a, the second LEDs 16c, and the red, green, and blue LEDs of the third LEDs 16c are individually addressable (per channel).

In accordance with the present invention, the carrier 12 is folded along the first and second longitudinal fold lines 15a-b so as to form a three-sided structure. The carrier 12 is preferably folded into a triangular shape, as illustrated, for example, in FIGS. 1-2 . The triangular shape may have equal sides. The carrier 12 is folded so that the surfaces 20a-c with the different LEDs 16a-c form the outer sides of the three-sided structure/triangular shape. The carrier 12 is typically folded during the manufacture of the LED filament 10, as will be discussed later in conjunction with FIGS. 7-9 .

By folding the multi-channel LED filament 10 into a triangular shape, the appearance of the LED filament 10 becomes smaller. That is, the dominant width of the LED filament 10 is always that of one of the carrier portions 14ac, i.e., width w, regardless of the viewing angle. In addition, interference is significantly reduced. That is, when the LED filament 10/carrier 12 is folded into a triangular shape with equal sides, the three portions 14a-c will be equally divided at an angle of 360°. The emitted light directions 18a-c can also be divided into 360° (each having 120°), resulting in minimal influence on each other. In particular, the blue light emitted by the third LEDs 16c will not influence the phosphors of the first and second encapsulants 24a-b for CW and W<w>, respectively. As a result, the LED filament gamut can be prevented from being reduced (especially in the blue corner), many colors (especially colors with blue content) being poorly reproduced, the color rendering index (CRI) being low, the light from the LED filament generally lacking in the blue and cyan parts of the spectrum, etc.

Turning to Figures 3-5, each of the first elongated carrier portion 14a and the second elongated carrier portion 14b (i.e., each of the outer carrier portions 14a-b) comprises notches 26 configured to allow the LED filament 10 to be arranged in a non-straight configuration, e.g., a helix as shown in Figure 5. By means of the notches 26, the folded carrier 12 may be folded into the non-straight configuration without deformation. The notches 26 may be cut from the carrier 12, typically during manufacturing of the LED filament 10.

The notches 26 in the first elongated carrier portion 14a may extend from the (first) longitudinal edge 28a toward - but preferably not to - the first longitudinal fold line 15a. Likewise, the notches 26 in the second elongated carrier portion 14b may extend from the (second) longitudinal edge 28b toward - but preferably not to - the second longitudinal fold line 15b. In particular, the first and second electrical circuits 22a-b may be drawn so as to taper off toward the fold lines 15a-b flush with the notches 26, such that the electrical circuits 22a-b avoid the notches 26. Furthermore, the notches 26 may be V-shaped, pointing to the first and second longitudinal fold lines 15a-b, respectively. Furthermore, the notches 26 may be placed at regular intervals I along the length L of the carrier 12.

The size and shape of the notches 26 as well as the distance I to the next notch 26 are determined at least by the radius of curvature of the LED filament 10, for example, the radius of the circular helix shown in Figure 5. In case of a radius of 10 mm (i.e., an inner diameter of the helix/spiral in Figure 5 of 20 mm), each notch 26 could have a depth d of 1.25 mm and an angle a between the legs 30a-b of 28°. The distance I to the next notch 26 can be 7 mm. With these dimensions, the legs 30-b of each V-shaped notch 26 meet in the middle when the LED filament 10 is bent over a diameter of 20 mm. The result is a smooth bending curve of the LED filament 12 and the gap of each notch 26 is closed.

Due to the notches 26 in the first and second elongated carrier portions 14a-b, the aforementioned first and second encapsulants 24a-b may be segmented. That is, a first encapsulant segment 24a' for at least one of the first LEDs 16a may be provided between every two subsequent notches 26 of the first elongated carrier portion 14a. In Figure 3, the first encapsulant segment 24a' covers three first LEDs 14a. Likewise, a second encapsulant segment 24b' for at least one of the second LEDs 16b may be provided between every two subsequent notches 26 of the second elongated carrier portion 14b. In Figure 3, the second encapsulant segment 24b' covers three second LEDs 14b.

Along with closing the gap of the notches 26 by folding the LED filament 10 into, for example, a helix/spiral shape as discussed above, the gap(s) between the first encapsulant segments 24a' and the gap(s) between the second encapsulant segments 24b' are also closed. This results in two (substantially continuous) first and second encapsulants 24a-b when the LED filament 10 is viewed. In other words, the first encapsulant segments 24a' may form a (substantially continuous) first encapsulant 24a covering the first LEDs 16a and the second encapsulant segments 24b' may form a (substantially continuous) second encapsulant 24b covering the second LEDs 16b when the LED filament 10 is arranged in the non-straight configuration.

Figure 6 shows a lamp 100 comprising two of the multi-channel LED filaments 10 each arranged in a helix/spiral shape. The LED filament(s) 10 will typically be folded into the helix/spiral shape during assembly of the lamp 100. The LED filaments 10 here form a double 3D spiral around a pump stem 102 of the lamp 100. The lamp 100 may further comprise a light transmitting envelope 104 surrounding the LED filaments 10, and a connector 106 for electrically and mechanically connecting the lamp 100 to a socket (not shown). The envelope 104 is preferably made of glass. The envelope 104 may have various shapes. The connector 106 may be of various types known per se, for example E26 or E27. The lamp 100 may further comprise a controller (not shown) for individually controlling the channels of the LED filament(s) 10. The lamp 100 may be, for example, a replacement bulb.

Figure 7 is a flow diagram of a manufacturing process of LED filament 10.

The method comprises step S1 of providing the unfolded carrier 12 having the first, second and third LEDs 16a-c, as shown in Figure 8. This step may include cutting the notches 26 in the first and second outer elongated carrier portions 14a-b.

The method further comprises step S2 of folding the carrier 12 at the first and second longitudinal fold lines 15a-b into a three-sided structure, for example a triangular shape, as shown in Figure 9. The carrier 12 may be folded with the aid of a bending mold. By heating the longitudinal fold lines 15a-b with a laser or thermophone, the material of the carrier 12 is locally melted. The material at the molten fold lines 15a-b that was deformed in this way will maintain the position after releasing the bending mold.

Optionally, the folded carrier 12 may be perforated by holes 32 along the first and second longitudinal fold lines 15a-b in step S3, see also Figure 4. This may release tension on the fold lines 15a-b. The holes 32 may be achieved by the use of laser cutting.

The LED filament 10 may further be arranged in a non-straight configuration in step S4, for example by bending the folded carrier 12 into, for example, a helix/spiral shape.

Those skilled in the art realize that the present invention is in no way limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

Furthermore, variations of the described embodiments can be understood and carried out by one skilled in the art in practicing the claimed invention, from a study of the figures, the description, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims (14)

1. An LED filament (10), comprising: a carrier (12) comprising a first elongated carrier portion (14a), a second elongated carrier portion (14b) and a third elongated carrier portion (14c) arranged side by side, the third elongated carrier portion being provided between the first elongated carrier portion and the second elongated carrier portion; first LEDs (16a) mounted on a first surface (20a) of the first elongated carrier portion to provide the first LED filament light (18a); second LEDs (16b) mounted on a corresponding second surface (20b) of the second elongated carrier portion to provide second LED filament light (18b); and third LEDs (16c) mounted on a corresponding third surface (20c) of the elongated third carrier portion to provide third LED filament light (18c), characterized in that the carrier is folded along a first longitudinal fold line (15a) separating the first elongated carrier portion and the third elongated carrier portion and along a second longitudinal fold line (15b) separating the second elongated carrier portion and the third elongated carrier portion into a three-sided structure, and in that each of the first elongated carrier portion (14a) and the second elongated carrier portion (14b) comprises notches (26) configured to allow the LED filament to be arranged in a non-straight configuration. 2. An LED filament according to claim 1, wherein the third LED filament light (18c) has a different spectrum than the first LED filament light and/or the second LED filament light. 3. An LED filament according to claim 1 or 2, wherein the carrier is folded into a triangular shape. 4. An LED filament according to any one of the preceding claims, wherein said first, second and third surfaces form the outer sides of the three-sided structure. 5. An LED filament according to any of the preceding claims, arranged in the non-straight configuration. 6. An LED filament according to any of the preceding claims, wherein the non-straight configuration is a curved configuration, such as a ring, a 2D spiral, a 3D spiral or a helix. 7. An LED filament according to any of the preceding claims, wherein the notches are placed at regular intervals (I) along the length (L) of the carrier. 8. An LED filament according to any preceding claim, wherein each notch of the first elongated carrier portion extends from a first longitudinal edge (28a) of the first elongated carrier portion toward the first longitudinal fold line, and wherein each notch of the second elongated carrier portion extends from a second longitudinal edge (28b) of the second elongated carrier portion toward the second longitudinal fold line. 9. An LED filament according to any preceding claim, wherein each notch of the first elongated carrier portion is V-shaped and points to the first longitudinal fold line, and wherein each notch of the second elongated carrier portion is V-shaped and points to the second longitudinal fold line, wherein preferably the legs (30a-b) of each V-shaped notch meet when the LED filament is arranged in the non-straight configuration. 10. An LED filament according to any preceding claim, wherein a first encapsulating segment (24a') for at least one of the first LEDs is provided between every two rear notches of the first elongated carrier portion, and wherein a second encapsulating segment (24b') for at least one of the second LEDs is provided between every two rear notches of the second elongated carrier portion, wherein preferably the first encapsulating segments form a substantially continuous first encapsulant (24a) covering the first LEDs and the second encapsulating segments form a substantially continuous second encapsulant (24b) covering the second LEDs when the LED filament is arranged in the non-straight configuration. 11. An LED filament according to any one of the preceding claims, wherein the first LED filament light is white LED filament light, wherein the second LED filament light is white LED filament light of a different color temperature than the white LED filament light, and wherein the third LEDs are RGB LEDs for emitting the third color LED filament light. 12. An LED filament according to any one of the preceding claims, wherein the width (w) of each of the first, second and third elongated carrier portions is in the range of 1 - 3 mm, preferably 1.2 -1.5 mm. 13. A lamp (100) comprising at least one LED filament (10) according to any one of the preceding claims. 14. A method of manufacturing an LED filament (10) according to any one of claims 1 to 12, wherein the method comprises: provide the carrier (12); and folding the carrier along the first and second longitudinal fold lines (15a-b) into a three-sided structure, for example, a triangular shape.